JPH033370A - Semiconductor sensor - Google Patents

Abstract

PURPOSE:To obtain a device capable of precisely detecting in a wide range of physical external force such as acceleration, contact pressure, atmospheric pressure and mechanical vibration and excellent in temperature characteristics, by arranging a plurality of FETs having different characteristics at a part where stress develops when a distortion member which is deformed by external force is deformed. CONSTITUTION:The title device is provided with the following; a retaining body, a distortion member which is fixed to the retaining body and deformed by physical external force, and semiconductor elements arranged at a part where stress develops when the distortion member is deformed. In the semiconductor sensor detecting external force by using the change of electric characteristics of the semiconductor elements, a plurality of field effect transistors having different characteristics are used as the above semiconductor elements. For example, a crystal growth layer 2 is formed on a semiconductor substrate 1; the semiconductor substrate 1 and the crystal growth layer 2 are eliminated in the form of an approximate OMEGA type; the central part is formed in a cantilever 3 as the distortion member; in the tip part of the cantilever, the semiconductor substrate 1 is left to constitute a weight 1G; in the base end part of the cantilever 3, a pair of MESFETs Q1, Q2 as the semiconductor elements for stress dection are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor sensor for detecting physical external forces such as acceleration, tactile pressure, atmospheric pressure, and mechanical vibration.

[Conventional technology]

Conventionally, as a technology in this field, for example, Japanese Patent Application Laid-open No. 6
The one shown in Japanese Patent No. 2-213280 is known. In this conventional sensor, acceleration is detected electrically by forming a cantilever with a semiconductor substrate made of silicon, and providing a semiconductor resistor as a piezoresistive element at the base end by diffusion. . Additionally, there are two types of cantilevers, one for acceleration detection and one for temperature compensation, in an effort to improve temperature characteristics.

[Problem to be solved by the invention]

However, the conventional device described above uses the piezo effect to convert changes in stress into changes in resistivity.
Highly sensitive sensors cannot be obtained. Also, the dynamic range is not sufficient. Furthermore, since a cantilever for temperature compensation is separately provided, a temperature difference is likely to occur between the cantilever and the cantilever for acceleration detection, and in such a case, temperature compensation becomes extremely insufficient.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a semiconductor sensor that can accurately detect physical external forces such as acceleration, contact pressure, atmospheric pressure, and mechanical vibration over a wide range and has excellent temperature characteristics.

[Means to solve the problem]

A semiconductor sensor according to the present invention includes a support, a deformable member that is fixed to the support and deforms when a physical external force is applied, and a semiconductor element that is provided at a portion where stress is generated when the deformable member is deformed. and detects the above-mentioned external force based on a change in the electrical characteristics of the semiconductor element, in which the semiconductor element includes a plurality of field effect transistors (e.g., Ga As-MESFETs) arranged in different directions with respect to the direction in which stress occurs. It is characterized in that it is made to be.

[Effect]

According to the configuration of the present invention, two FETs are provided so that the arrangement directions are different in the parts where variable members such as the cantilever beam for the acceleration sensor and the diaphragm for the pressure sensor change, so that one The electrical characteristics of one FET change greatly due to stress due to deformation, while the other FET's electrical characteristics do not change much. Therefore, physical external force can be detected with high accuracy.

Further, since the two RETs do not need to be provided at different positions, the temperature difference between the FETs can be reduced and the temperature characteristics can be improved.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view of a semiconductor sensor according to an embodiment of the present invention. As shown in the figure, a crystal growth layer 2 is formed on the upper surface of a semiconductor substrate 1 by an epitaxial growth method, and the semiconductor substrate 1 and crystal growth layer 2 are removed in a substantially Ω-shape, and the central portion is cantilevered as a deformable member. It forms beam 3. The semiconductor substrate 1 remains at the tip of the cantilever beam 3 to form a weight IG, and a pair of MESFETQl is installed at the base end of the cantilever beam 3 as a semiconductor element for stress detection.

Q2 is formed. Further, a signal processing circuit 4 is formed in a portion of the crystal growth layer 2 other than the cantilever 3 (support portion), and is connected to the FETs Q and Q2 by a signal line 5.

FIG. 2 is a circuit diagram corresponding to the configuration of FIG. 1.

FETQ and FET formed at the base end of the cantilever beam 3
The Q 2 drain is connected to I/V conversion circuits 51 and 52 each having an amplifier A and a feedback resistor R, and the output of the 1/V conversion circuit 51 and 52 is input to a differential amplifier circuit 53. Then, a signal OUT corresponding to the difference is output. Here, FETQ and Q for stress detection are arranged in different directions. Specifically, FETQl is in the direction perpendicular to the stress direction and the longitudinal direction of the gate, and FEIQ2 is in the direction in which the stress direction and the longitudinal direction of the gate are parallel. It becomes.

Figure 3 +1FETQ, Q (7) I-V characteristics,
S2 Shows temporal changes due to dress. In addition, the horizontal axis v
, ■ are FETQ and Q de-DSL, respectively.
DS2 1 2 Indicates the voltage between the drain and the source, and the vertical axis is IDS□.

Summer is drain number DS2 of FEIQ and Q, respectively.
1 2 Indicates the current between sources. The FETs Q and Q are formed with the same specifications, so their IV characteristics are essentially the same, as shown by the solid lines in FIGS. 3(a) and 3(b). In such a case, the cantilever beam 3 deforms and the FET
Suppose stress is added to Q and Q2. Then, F
In ETQ1, since the direction of the gate electrode and the direction in which stress is applied are perpendicular to each other, changes in the IV characteristics due to the piezoelectric effect appear largely as shown by the dotted line in FIG. 3(a). On the other hand, in FEIQ2, since the gate direction and the stress direction are parallel, the change in the IV characteristic appears small as shown by the dotted line in FIG. 3(b).

Then, in Fig. 2, the current 1.12 flowing into each of the two amplifiers A becomes ■1>■2 (for example, ■ = v 212), which is converted from I/V to voltages V and V2 in the differential amplifier circuit. 53. The differential amplifier circuit 53 takes the difference between the voltages V and V2 and amplifies it, so that the output OU of the differential amplifier circuit 53
T becomes a signal corresponding to the stress applied to FETQ, Q2.

In this way, according to the present invention, the FET's I-
This causes a change in V characteristics, and this change is extremely sensitive. Therefore, a sensor with extremely high sensitivity can be realized.

Also, FETQl.

Since both FETs Q2 are formed at the base end of the cantilever beam 3, temperature changes occur in almost the same way in FETs Q and Q2, resulting in extremely good temperature characteristics due to temperature compensation. It goes without saying that this temperature characteristic is better as the FETs Q and Q are 2 closer together.

Furthermore, as in the example, the cantilever is made of a compound semiconductor, and MESFETs Q and Q2 for stress detection are formed in the stress-generated portion of this compound semiconductor,
Furthermore, if the signal processing circuit 5 for processing the output signal is formed in the crystal growth layer 2 made of the same compound semiconductor, the structure of the semiconductor sensor can be made extremely compact.

Furthermore, a circuit formed in a compound semiconductor such as GaAs can operate satisfactorily even in a high temperature environment and can perform signal processing at high speed, making it possible to provide a highly sensitive semiconductor sensor with excellent environmental resistance.

The present invention is not limited to the above embodiments, and various modifications are possible.

For example, it may be applied to a diaphragm as shown in FIG. As shown in the figure, a portion of the semiconductor substrate 1 is removed to form a diaphragm 8 made of a crystal growth layer 2.

At the end of this diaphragm 8, there is a MESFETQ
, Q2 are formed. Here, the gate direction of FETQl is perpendicular to the stress direction, and the gate direction of FETQ2 is parallel to the stress direction, so FETQ
The IV characteristics of l change more significantly in response to stress. Therefore, by implementing the circuit configuration shown in FIG. 2 using the signal line 5, similar effects can be achieved. Also,
FETs for stress detection are not limited to Schottky gate type ones.

〔Effect of the invention〕

As explained above in detail, according to the present invention, two FETs are provided in the portion where the deformable member changes so that the arrangement directions are different, so that the electrical characteristics of one FET change due to the stress caused by the deformation. changes significantly, and the other FET
doesn't change much.

Therefore, physical external force can be detected with high accuracy. Also, 2
Since the individual FETs do not need to be provided at separate locations, the temperature characteristics can be improved. Therefore, according to the present invention, it is possible to realize a semiconductor sensor that can accurately detect physical external forces such as acceleration, contact pressure, atmospheric pressure, and mechanical vibration over a wide range, and has excellent temperature characteristics.

1... Semiconductor substrate, IG... Weight, 2... Crystal growth layer, 3... Cantilever beam, 4... Signal processing circuit, 51.
52... I/V conversion circuit, 53... Differential amplifier circuit.

Claims (1)

[Claims] 1. A support body, a deformable member that is fixed to the support body and deforms when a physical external force is applied, and a portion where stress is generated when the deformable member is deformed. In a semiconductor sensor that detects the external force by a change in the electrical characteristics of the semiconductor element, the semiconductor element has a plurality of electric field effects arranged in different directions with respect to the direction in which the stress is generated. A semiconductor sensor characterized by being a transistor. 2. The semiconductor sensor according to claim 1, wherein the field effect transistor is a Schottky gate field effect transistor formed in a piezoelectric semiconductor.